A How to Know Guide for Derek Shepherd
by RulerOfAllThatIsEvilChiFlowers
Summary: Ways to know if your significant other and best friend are into each other. A collection of OneShots that should've warned Derek that there might have been an attraction between Addison and Mark. Addison/Derek/Mark #Maddek #Maddison #Addek
1. (1)

**A How To Know Guide for Derek Shepherd:** _Ways to know if your significant other and best friend are into each other. . . ._

* * *

 _#1_

It's a pretty pretty clear indication that your girlfriend and best friend are into each other if they quarrel ... _Quarrel?_ ... Yes, if they quarrel like jealous lovers.

It was a Monday afternoon, and Mondays are usually when the 'Montgomery' in Addison Montgomery, blares out like a rabid beast. Because, you know, it's Monday and nobody in their right mind ever really like Mondays. _Nobody_. So, like most Mondays, if not all, and that particular Monday, she was in one of her 'moods' when she and Derek met up for coffee after their day at Columbia had ended.

She yelled at the cab driver for stopping at the junction of Amsterdam and 113th Street to let a frumpy old couple - _'freaking Jersey slowpokes'_ as she so eloquently put it, cross the street.

In Addison's opinion if you can't walk fast enough, then don't walk at all.

Well, he can't really fault her for speaking her mind out loud and unnecessarily so, he must add, because they're in New York City after all.

 _What's that they say about New Yorkers?_

He, also, didn't tell her to calm down because he didn't need to get on her bad side on a Monday.

Tuesdays, maybe. And Wednesdays, definitely. But never Mondays.

He's been there and surprisingly, he survived.

She insulted the barista's deplorable latte-making skills at the cafe, asking him if he'd learnt to make coffee in some sort of penal reformatory institute.

Derek can only hope the guy hadn't spit into their coffees. He did look slightly infectious with the dark circles and waxy veneer.

She glowered at the waitress at the restaurant when she came over to check if there was anything else that they needed. Addison had told her that if there was, she'd be the first to know, but in the meantime and because she'd have better luck there too, she should just return to her regular job of working the streets 42nd and Murray Hill, instead of making googly eyes at her boyfriend.

His eyes grew wide in shock when she said that. And he reddened in embarrassment for Addison's colourful way of words.

 _What's gotten into his angel who wouldn't hurt a fly?_

This - the Montgomery beast, her mood - isn't like her. It's got to be more than just hating Mondays.

Derek, himself, couldn't seem to do or say anything right as well. Addison didn't exactly yell or insult him, that behaviour was only reserved for people she's not quite fond of and besides it wouldn't fit into her picture of how a perfect girlfriend should act, even when piqued. But when Derek asked her how her parents were doing, she thinned her lips. When he told her how pretty she was looking, she only sighed. And when he asked her if she had had a good weekend ( _he had been in Rochester visiting his grandmother._ ), she just glared at him and looked as though she wanted to scratch his eyes out.

Derek didn't have a clue what was the matter with her. Obviously something was wrong, but he knew better than to ask what. He'd learn from Mark that you should never ask a woman what's wrong.

They might tell you. And that's just like opening Pandora's box.

He discreetly tried to survey her boobs to see if they were bigger than usual, speculating that raging hormones might be to blame.

 _Oh god! What if she's pregnant?_

Unfortunately, he wasn't discreet enough. She had caught him and crossed her arms over her chest and glared at him from across the table.

"Are you done staring at my breasts, Derek?" she arched a brow, "Stop it, will you? You're not a horny teenager anymore! We need to actually start the proposal for our SP. The due's in two weeks from now and I'd like to make sure I have your full attention." Addison questioned waspishly.

"Huh?" he replied in a daze, dragging his eyes to her face. "Oh, um, yeah, of course." he finished sheepishly.

She pursed her lips and took on a distinctly school marm-ish expression. Derek had a feeling that at any moment now, she would produce a ruler and rap him over the knuckles with it for his inattention.

"God! Don't boys ever think about anything else other than sex?" she asked in disgust.

"In my experience, no." a familiarly deep drawl interjected from behind Addison.

Mark had appeared without attracting either Derek or Addison's attention. He easily insinuated himself into the seat between them, eyes never leaving Addison's face, which was contorted with even more contempt and hostility than she'd displayed to the unfortunate waitress earlier.

Derek was amazed at how calm and detached Mark could remain in the face of such wrath. Addison's rage at Mark's sleazy demeanour had obviously extended beyond its usual level, yet the other boy did not even blink. His smirk was still fixed firmly in place.

"I especially think that it is highly unlikely you would find a boy, or for that matter a fully-grown man, capable of thinking of anything else when they have a gorgeous redhead before them in a skirt and thigh highs." Mark continued, leering at Addison's legs. "You might want to get used to it, Red."

Now normally this was the sort of comment that Addison would pretend to hate but secretly love, because she accepted it as the compliment Mark intended it to be. They're only acceptable coming from Mark. But instead of slapping him and telling him he was heinous or disgusting ( _all the while wearing a small, secretive smile._ ), she continued to regard him with icy contempt.

"Was there something you wanted, Sloan?" she enquired coldly. "Or are you simply so starved for company you've decided it's no longer rude to interrupt private conversations?"

Mark's eyes narrowed at her asperity. Derek was kind of surprised himself. He knew Addison was in a bad mood, _obviously_ , but if anything Mark was the one who could normally be counted on to lift her out of the doldrums.

Oh, they do argue. They always always bicker. Fairly frequently, in fact. But it was always with an air of banter and mockery as they tried to bait and one-up each other in a kind of friendly rivalry that had developed between them. Not with this undercurrent of genuine antagonism now emanating from Addison.

"Oh, I think you know I'm never short of company, Red." he countered curtly, eyes still trained intensely on Addison, barely seeming to even register Derek's presence. "As it so often happens I do frequently find myself double-booked."

This words seem to have a jolting effect on Addison. Her spine straightened and she suddenly affected a look of indifference. Yet there was a definite frission of tension in the air. Derek had the distinct feeling that his best friend and girlfriend were speaking in some sort of code impossible for him to understand, meaning more with their words than what they were actually saying.

"What are you doing here, then?" she asked nonchalantly. "We wouldn't want to take up any of your valuable free time." Her tone was diabolically, derisively sweet.

Derek decided it was time he interposed and defused the situation. "Actually, I asked Mark if he wanted to join us this morning. I was away for the weekend, so I thought we could all get together. Sorry I forgot to mention it."

Mark's eye contact with Addison was finally broken as he turned towards Derek, ending whatever cryptic communications had been passing between the two.

She also transferred her attention back to her boyfriend. She rolled her eyes.

"Lovely. You decided to invite your best friend on our date. How romantic."

Derek's forehead creased. _Hmm, maybe that_ _had_ _been kind of dumb_. "Well, you've never minded before." he pointed out feebly. She had always seemed more than happy to have Mark hang out with them.

When he added up the pros and cons of their relationship, it was one of the things he had always liked best about Addison, that she got on so well with his best friend. It had to say something about their compatibility as a couple.

 _Right?_

Mark's attention was taken up by the waitress taking his order. He paid his usual flirtatious attentions to the girl, but having received her warning from Addison earlier, she did not respond. Nevertheless, Addison seemed to find something offensive in the spectacle and when she spoke again it was with renewed venom.

"Did it ever occur to you I don't _always_ want to be hanging out with your jackass of a best friend." Addison hissed in a low voice as she leant across the table to Derek.

"Well, I honestly didn't think it would bother you. I mean I figured you hadn't seen him for a couple of days either while I was away, so I thought we could all ... you know ... catch up." Derek floundered.

She sat back in her chair, her face now clouded with a different emotion. She seemed embarrassed. And maybe ... guilty?

"Actually, Addison and I were supposed to spend the day together yesterday." Mark cut in smoothly. "But I'm afraid my Saturday appointment continued into the better part of Sunday and it somewhat wrecked our plans."

This was all relayed dispassionately, as if being of little interest. But taking in Addison's wan face and telling silence, Derek suspected this was the real source of her beastly mood.

"Oh" said Derek lamely. He'd never imagined that Mark and Addison would elect to spend the day with each other while he was away. Not that there was anything wrong with it. It just never occurred to him.

He quickly changed the subject by launching in to a recital of the things he'd done over the weekend. Mark had cooperated by offering the occasional witty remark or conversation filler.

Although it might have been evident to the more observant that there was a somewhat false note to the encouraging smile plastered on his face, and that he kept shooting covert glances at the still-silent Addison. Eventually though she too rejoined the discussion, albeit addressing all her comments only to Derek.

Finally, somewhat exhausted from his unusual role of being the most talkative member of the gathering, Derek excused himself from the table.

He procrastinated on his visit to the gentlemen's facilities, hoping to give Mark and Addison sufficient time to sort out their differences. Lingering as long as he could without raising suspicions that he was suffering from some sort of food poisoning.

As he re-entered the restaurant, he paused behind a Venetian screen that would shield him from Mark and Addison's view but enable him to listen in on their conversation, so he could determine if it was an apposite time for him to return to the table.

Judging from their crisp tones, it would seem it was not.

"Look, I've already said I was sorry, Addie." Mark said in a way that made him sound like he was not really sorry at all. "Maybe if you and Derek ever get around to do more than just hold hands, you'll realise it's easy to lost track of time in certain situations."

"Well, I would have expected you to be more respectful, that's all." Addison answered snidely. "The skanks you sleep with do charge by the hour, don't they?"

"Your bitchy side is showing, Red." Mark snapped. "And anyone can see the real reason why. You're freakin' jealous. And it's not a pretty colour on you."

"Oh, yes, I'm positively seething with envy for the poor girl you connived and seduced into your world of hedonistic exploitation. I so wish it was me who is having to worry about being tested for various STDs this week."

"I guarantee she had a better time than you did yesterday ... seething because I broke our plans."

"I did not seethe and I don't rely on you to fulfil my days. I have a handsome boyfriend who just so happened to be away over the weekend, and therefore no reason to be jealous. And when you failed to show, it wasn't hard to find someone to take your place. But, as you pointed out, you did break our plans and I just happen to find that incredibly rude."

"Forgive me if like any red-blooded male I enjoy having sex more than spending an entire day with you eating gelato, caviar and whatever else you rich people eat and watching movies so ancient that Grandma Montgomery wasn't even born yet."

Derek knew this had been Addison and Savvy's ritual before the blonde got herself a new distraction. He hadn't realised that Mark had taken over the tradition, in addition to the other ways he'd assumed the role of surrogate best friend.

"Well, don't worry, if my company is so _awful_ , I'll be sure not to inflict myself on you again." Addison's livid tone had become more of a sob.

Mark seemed to soften slightly in response. "C'mon, Addie, you know _awful_ is the last thing I consider you. Except maybe sometimes when you're going on and on and on about what it would mean to marry into the Shepherds'."

She snorted. "Now, look who's being jealous?"

Mark continued. "I've broken plans with other girls a number of times to come to the rescue in one of your so-called emergencies. And it wasn't the girl that kept me in bed yesterday so much as the massive hangover I was recovering from the night before."

"I don't care. Like I said, it's not the girl. It's about you being an unreliable bastard who can't be counted on to be there when someone actually needs him."

"What the hell is that supposed to mean? I presume you know how to work the DVD player without me."

Silence from Addison.

Mark seemed to realise maybe there was something going on here that he didn't understand either. "Why? Why was yesterday so important to you?"

"I ... I just wanted to talk to you ... about something." Addison muttered. "But you know what, I'm glad that I didn't. I'm glad you reminded me what an insensitive ass you are. Just forget it. I'll never trouble you with my problems again."

Derek heard her chair being pulled back across the tiled floor.

"Addie, c'mon ..."

"Tell Derek I had to go and to don't bother coming over ... Just ... I'll see you tomorrow, Mark."

With that, she rushed out of the restaurant, not even seeing Derek as she passed him, tears already forming in her eyes.

When he came back to the table, Mark said that Addison had had to go home to study. He made no reference to the length of time Derek had been gone. He did not seem to have noticed.

Derek felt sorry for his best friend. Sure, he and Addison had had their own share of problems, but they'd never had a fight like that. He couldn't think of any other time he'd seen Addison so passionately enraged either.

He barely registered the fact that there was a small part of himself that was secretly quite pleased at the prospect of a rift between his girlfriend and too-charming best friend.

 _Addison and Mark?_

There's a higher probability that he'd get struck by lightning instead.

* * *

 ** _What do you guys think of this idea for a one shot? Yea or Nay? Let me know. :) REVIEW!_**


	2. (2)

**A** **How To Know Guide for Derek Shepherd:** _Ways to know if your significant other and best friend are into each other. . . ._

* * *

 _#2_

If you catch them confessing their love for each other, it might as well be that your girlfriend and best friend are actually ... you know ... _in_ _love_ with each other.

The car sped along the highway as they head back to the city at the end of the summer, away from the carefree sun, sand and sea of the Hamptons, and into the most brutal, gruelling and unpleasant year of medical school - the final year - one that will be commencing tomorrow.

They haven't enjoyed any of their summers since entering hellish schedules and competition and had thought - _what the heck!_ They deserve a little fun after all the blood, sweat and many _many_ tears that they've graciously invested in the name of science. So, one summer with a group of friends can't hurt anyone and, of course, their future.

The thing is they're not ready. For the future, that is. None of them are and it's so surreal how life is happening and going by so quickly. Too quickly for their liking because now, as they realised, tomorrow will be another day, when over twelve hours ago, today had just commenced.

Three _about to be doctors in a year's time_ lay sprawled on the backseat with Derek listening to his Walkman, hands clasped together on his lap, eyes closed and feet up. He could be sleeping for all anyone's concerned. It's near impossible, if not totally, to tell if he's even awake.

On the other end, sat Mark, apparently engrossed in the Financial Times.

 _Who knew he would ever take interest in the stock market?_

Between them, as ever, was Addison. Miffed that Derek would prefer listening to his device to having a conversation with her, and amidst her sulking with her arms crossed and muttering, "I can't believe you chose _that_ ... thing over me. I'm Addison. That means something." under her breath, she had surely exhaust herself to sleep. And as they drove an over two hour ride back to the city, her head lulled onto Mark's shoulder.

 _Uh-oh ..._

He froze, eyes widen in fear, like a man would in his predicament. This isn't going to end well - _no, no, not for him, at least._

 _What to do? What to do in a situation like this?_

He's panicking.

 _Should he lean more onto the door? Should he wake her up? Should he push her off? Should he move her head onto Derek's shoulder instead?_

But he doesn't want to do any of that. He likes her head there, on his shoulder.

So, he opt to not move and he didn't since the second her head did that thing on his shoulder.

 _But how can he concentrate on the price of the Dow when his senses are being assaulted by the sweet indulgent smell of her hair?_

 _S_ he smell of tropical - a whiff of heavenly mango and coconut and ... and something else quite endearing and exciting, one that he can't pinpoint.

Maybe he could buy her an entire set of beauty products for her birthday.

But he hasn't the slightest clue of this particular brand that she's using. Plus he don't think he can afford the luxury she uses. She's Addison Montgomery after all. But, of course, the price will definitely be worth it all because at the moment, he damn well is enjoying the intoxicating heaven that is her hair.

He'll figure something out. He probably will just set some cash aside.

But mixed into that heaven is a good dose of hell, because he shouldn't be sniffing and breathing in the smell of his best friend's girlfriend's shampoo like some lovesick teenager. He shouldn't be marvelling at how soft and warm her skin feels where it's resting against his. He really _really_ shouldn't be fantasising about the things he would love to do to her in the back of this car ... if only Derek wasn't here.

He mentally slapped himself. This isn't like him. Not at all.

Mark Sloan do not do yearning.

He simply takes what he wants, does whatever he desires, no questions asked.

But ... but with one exception, he thought with a grimace, and that exception is a five-foot-ten redhead with lips so red a man can't help but imagine doing wicked things to them.

So what, she's hot, he reflected dismissively. Beautiful even. _Gorgeous actually_. Manhattan is filled with hot, beautiful, gorgeous women, most of whom were only too eager to indulge in his most lurid fantasies. He had no cause to regret the off-limit status of a Connecticut princess.

She's Addison, prim and proper and perfect, it only makes sense that she's with someone who's just as genteel as she is.

She's very off-limits.

And it doesn't matter how much she makes him laugh, doesn't matter that she has an uncanny knack for always knowing exactly what he was thinking, it didn't matter that she has always been there for him, ever since Derek introduced her to him, ever since they became ... somewhat friends.

She isn't for him.

 _And what the heck is a playboy like him wondering what to get a girl for her birthday, anyway? Especially when said birthday is months and months away?_

He probably wouldn't buy her anything at all, he thought mulishly. His presence at her party alone should be gift enough.

It's just that he's infatuated by the forbidden. He can't have her, so he's craving for her. He has to have her somehow and in someway. The element of taboo surrounding her, both because of who she is and who she is with. Because even if she wasn't in a relationship with his best friend, she still would have been beyond his reach.

Because Addison is a quality girl, respectable and classy. She's elite with a trust fund. And he's none of those - the complete opposite, actually. And he's nothing like Derek who can accommodate all of those lacking.

Mark's pulse raced with the thought as a familiar ache filled his groin.

 _Christ, how does Derek not please her twenty-four-seven?_

Every time he thought about her, he just want to drag her onto his lap, clamp his mouth on hers and mark her as his own, like the conqueror of a new land.

To violate her perfection with his imperfections.

He imagined what it would be like to be Addison's first non-preppy schoolboy. Knowing her, she'd probably approach sex with the same fiery determination to succeed that she shows in every other aspect in life. That could be ... quite wondrous and wild.

 _You know what they say about redheads - they're crazy in bed._

He wondered if she would be eager to learn all the things about physical intimacy that he would be only too happy to teach her.

 _Would she be interested to learning other pleasures?_

She grew up in sheltered Connecticut after all, so that, itself, ought to be a good enough reason as to why she needs lessons from him.

Mark envisaged the things he would teach her if she would let him. First, would be how to kiss. Derek never kissed her properly.

 _Well, it's not how he would kiss her._

He would show her that a true kiss will leave you breathless, heaving and trembling with passion. A true kiss will fill you with an insane need to get as physically close to the other person as humanly possible. Then, he would teach her how to touch - touch herself slowly, as she slides out of her clothes and expose herself to his hungry gaze, to touch him, hesitantly, wantonly, animalistically, until there is no part of his body that she does not know. After that, he would ask her to let him touch her - to stroke her, rub her, pinch her, lick her, suckle her - until she can bear it no longer.

He imagined Addison on her knees in front of him. In white lingerie - the colour of purity. But he'd teach her some very impure things. Very very impure indeed.

Mark didn't fight the erotic fantasies that began to steam inside of his head. It's safe to indulge them in the privacy of his own mind, he decides.

It's only natural that one does.

Suddenly and without him even realising, Addison was awake and stretching with feline grace, making the material of her top stretch taut across her breasts.

His eyes zeroed in on the sight.

Before she had time to recover from the dazed confusion of her first awakening, Mark laid the newspaper strategically over his lap. And to distract her further from what she's doing to his body, he drawled, "So, Sleeping Beauty's finally awake? I'll be sending you the dry-cleaning bill for drooling all over my jacket by the way."

She just glared at him groggily, in fact. Perfect, thin brows raised scowling at him and for a second he thinks he might just be terrified of her. And he was right because just then, she grabbed his collar and pulled him closer so their faces were only a hair's breath apart.

His heart stopped beating, then.

"Listen up, Sloan, I do not drool under any circumstances. Got it."

"You might want to take it down a decibel, princess." he whispered conspirationally. "Prince Charming is still napping." he motioned to Derek's recumbent form.

Addison let go of his collar, looking somewhat guilty.

"You're such an ass, you know." she hissed furiously.

Waking up just as she had, and from a dream so peculiar, so bewildering, and so unfitting about said person in this car that she can't even look at said person in the eyes anymore, that had left her so _so_ very confused, and when she's so very that, she tends to lash out at whomever was in close range.

Mark smirked at her.

"And only a week ago you told me you loved me." he drawled.

Addison reddened. Trust Mark to throw that moment of weakness back in her face with a smug. But two can definitely play at that game.

"As I recall, Mark, I was not the one who said it first." she replied sharply.

"Only because you practically begged me to."

And finally the elephant that has been living with them for the past few days have been addressed and acknowledged.

 **XXX**

Along with a few of their friends from Columbia, Mark, Addison and Derek had decamped from Manhattan to the Hamptons right at the beginning of the summer.

All had stayed at the Montgomery's residence. _Of course._ It was promised to be a truly halcyon summer. And for a few weeks it had been ... truly.

Derek had paid more than enough attention to Addison, complimented her a handful of occasions, and she was the envy of the other bikini-clad beach-loving socialites.

Mark had chased girls, and more often than not, caught them.

Derek had seemed more than content and happy to hang out with his girlfriend and best friend.

They had simply had fun, and the awkward moments and unwanted emotions on his part seemed to have been suppressed and is now long forgotten.

 _Good_.

Perhaps it never even existed in the first place.

Then, they bumped into Minka - one of Addison's preppy high school friends ( _though she kept insisting that their relationship never was that_.) in Southampton, who had invited them all to a beach bash at her beach house.

Addison was more reluctant, opposing to the invite without a single thought. But he brushed her off with a quick, "We'll definitely be there." at Minka, which undoubtedly resulted in a death glare and silence on Addison's part for the rest of the afternoon.

Just like with Derek, she can never stay too mad at him for too long. And he knew that.

It had turned into a true all-night rager.

In the early hours of the morning, someone had suggested skinny-dipping on the private beach. Some of the partygoers were all for it, others were more reluctant.

Derek - _oh, it wasn't even remotely a surprise_ \- had pointed out that the water would be pretty cold at that time of night and he wasn't about to freeze his ass off.

Minka and Tina had laughed and said he was chicken.

 _Oh ... but Derek is a realist. The water would be freezing._

Mark had of course said he would not be as ungallant as his best friend and would be happy to escort any naked lady who wished to go into the water. Or anywhere else for that matter.

Derek had persisted that it was a bad idea.

Then, Addison shocked the life out of both of them by unzipping her short summer dress so that she was clad only in bra and panties. And then she quickly kissed her boyfriend on the lips in an unmistakeable invitation and told him not to be a spoilsport.

"C'mon, Derek. It'll be fun."

The neutral feelings Mark had been trying so hard to maintain about Addison and her relationship with Derek collapsed. He could clearly see how the chain of events would unfold. Derek would first take Addison's hand and they would be off into the water, fingers intertwined. And, after swimming together au natural, they would return to the house, passions inflamed, then, one thing will lead to another and he'll be left to stuff his ears for the rest of the night.

He isn't quite sure how he feels about that, but it was definitely not neutral, absolutely not okay about it all.

Instead, Derek just shook his head at her, insisting that it wasn't a good idea, and gave her a kiss on the cheek, telling her to not go too far into the water. That he's just going to go back to her place and crash on the couch.

"Mark ..." Derek nodded at him before he walked away, which meant to keep an eye on Addison.

He nodded in response.

 _Of course, he will._

Just for a second, Mark caught the look of hurt and disappointment wash on Addison's face, before it was replaced with one of determination.

"So, are we going to do this thing, or what?" she asked as she turned back to the group.

"You know a real skinny-dip requires that you lose the underwear, right?" Mark drawled. He found it hard to believe that the prim and proper and perfect was amenable to swimming naked with more than a dozen of sweaty and drunk and hairy strangers.

"You know me Mark." she said, looking right into his eyes in a way that made his pulse race, "I never back down from a challenge." Then, she led the way down to the beach.

During the short walk, Mark's opinion on the advisability of a midnight skinny-dip started to shift.

From yes, all for it to, no, this is so stupid.

All sorts of possibilities started to form in his head. They never would have occurred to him in relation to his own - or anyone else's, for that matter - safety, but now he actually finally comprehended that Addison would be joining in on the escapade, that's making him increasingly anxious.

It was dark and they were drunk. It's a recipe for disaster. It would be easy for someone to get into trouble in the water, to drown even, without anyone noticing. And Mark had heard that sharks came closer to the shore at night. For all they knew the ocean could be filled with them. And the water will be so cold.

Derek Shepherd was right.

And Addison is slender with hardly any subcutaneous fat to keep her warm and the fact that she's always _always_ cold, regardless of the temperature, did not sit well with him.

She would feel the cold much worse.

"Addison, wait!" he began to call out.

But before he could catch up to her, she was already stripping off.

He only caught a glimpse of her before she was submerged in water. But that little glimpse was enough to make him momentarily forget he ever even had a friend called Derek Shepherd.

So too he made his way into the water with the others, most of whom were laughing and giggling with each other. Mark, however, was completely focused on Addison, who was floating a little further out.

She was staring up at the moonlight, seemingly lost in her own thoughts, a wry smile on her face.

"You are ..." he paused, searching for an adjective that adequately expressed how in awe he is of Addison Montgomery. "Amazing, you know that, Montgomery?"

She smiled sardonically and shrugged. "I sometimes think you're the only one who knows that."

"Derek doesn't know how to have a good time."

"Unlike you."

"Unlike _you._ " Mark corrected.

Addison stopped staring at the moon and turned to Mark.

"Some people think I'm no fun."

"Some people think veganism gives them psychic powers."

"You don't think I'm some prissy Stepford WASP who always has to colour inside the lines?"

Mark moved closer to Addison, dropping his voice to a confidential whisper. "Red, if you were really a girl like that you wouldn't be so naked right now."

Addison looked down at her body in surprise, as if she had just realised it's unclothed state. In the dark and under the water, nothing important was visible, just a vague shape and colour of flawless porcelain skin.

She then turned her attention to his body, realising that he too was also undressed. She could see his chest and both his arms, her breathing elongated.

Derek's arms aren't as muscular as Mark's and she just noticed them so strong and solid and she suddenly has the urge to run her fingers along them. His chest hairs are sticking out in different directions and she wondered if she could get them to lie flat with her tongue. She could probably use her tongue on his nipples too, which at the moment looked rock hard from the cold or something ...

She froze as the realisation dawned on her.

 _No way. No fucking way._

It's just that she had never paid much, if not any, attention to his ... immaculately chiselled body and it's ... it's ... making her blush with the unwavering thoughts roaring in her head. And if she wasn't so frozen, she'd be in flames right now.

"I'm drunk." she whispered in horror.

Mark grinned. "Endearingly so."

"You have to help me," she hissed, gripping his arm.

"Are you talking about the kind of ' _help_ ' that's going to cause problems between me and my best friend?" Mark whispered back, wondering what he would do if she would say yes.

Addison slapped his arm.

"Ow," he swore, rubbing his arm. "Okay. So, what is this help that you need?"

"I need you to get me back onto the beach and into my clothes without anyone seeing me naked."

"Any idea how I should go about achieving this mission impossible?"

"No. I'm drunk, remember?"

Mark thought for a minute. Truthfully, he really didn't want the other guys in the water - some lame-brain brats - to be ogling Addison when she gets out of the water, either.

"It's simple." he told her. "You just have to stay in the water until everyone else gets out and has gone back inside."

"But I'm already getting so c-cold." Addison whimpered.

Mark cursed. "Well, they will too, then." he said.

But then, he helped speed up the exit of Minka and Tina from the ocean, and consequently the rest of the guys, with some obnoxious underwater tickling and threatened drownings.

After Addison forced Mark to keep his eyes closed while she got out and put her clothes back on, he helped her back home on wobbly legs. It was a strange role reversal – normally it'd be she ( _and Derek too_ ) taking care of him after he'd get intoxicated at a party.

"Do you really think I'm fun?" Addison asked as they reached the little wooden gate to her beach house. His arm had been wrapped around her stomach to steady her and when she turned back to face him her mouth was only inches from his.

He looked into her eyes. "Sweetheart, you're so much fun that I just know you can't be good for me."

Addison arched her eyebrows. "You love things that aren't good for you." she whispered huskily.

"Yea." he murmured as his mouth descends to hers. Her breath was whispering shivers into his lips and he moved to tuck a strand behind her ear.

 _He does like things that aren't good for him._

 _He likes her._

"Great! You guys are back." Derek said congenially as he opened the door. "You both better get to bed and get some sleep. You're going to be feeling pretty sick in a couple of hours from now."

 _Shit!_

"Yea. Sure."

Addison was already turning the latch to the gate and he watched as she gave her boyfriend a kiss on the mouth, whispering something that he wants so desperately to hear, then disappearing into warmth without any acknowledgement of what almost just happened.

The next day Derek's prediction proved to be correct. Mark had a massive hangover while Addison's seemed to be compounded by a case of the flu, brought on by her late night swim.

She lay groaning under the pillow and covers when Derek first visited her with a morning pick-me-up and completely ignored his kind gesture, insisting that she just needed to rest her eyes a little more, that she wasn't at all ill.

Now, that she still is sick. "I better go get Derek. Tell him we won't be heading to the centre anytime soon." Mark said.

Just then, a knock was on the door.

"Don't let him in." Addison hissed, just as Mark was about to say " _Come in_."

"Why not?" he asked.

"I don't want him to see me all ... snotty and blotchy."

"Oh, right. I forgot that I'm the only one who has that privilege. Thank you for that." Mark moved towards the door before she had a chance to smack him with a pillow.

He and Derek had a hushed conversation outside.

"He's going to call a doctor. A real doctor. Not us." he informed Addison a few minutes later. "He said he's going to cancel plans with Sam and the others to stay here and nurse you."

She groaned again. "I don't want him to stay here with me."

"You're face really isn't that ... blotchy. You still look nice."

"It's not that. He'll be all annoyingly high and mighty and smug about being right about the skinny-dipping being a bad idea. And I don't want to put up with his 'I told you so' attitude all day. It's annoying."

Mark smirked. "I'll see what I can do."

Half an hour later of much convincing, he re-appeared with some plain toast and the news that Derek had been dispatched to play golf with Sam and the others.

Mark had opted to stay home with Addison. It was to nurse his own very persisting hangover, and definitely not her.

Nevertheless, he spent the next several days at home with her as she continued to feel sick.

It was only fair Addison said, pointing out that _she and Derek_ would keep him company when he fell ill countless of times.

He internally rolled his eyes. It's always Addison and Derek, she and Derek, never just _she_ , herself. They just have to conjoined by the hips.

 _Addison and Derek._

But he did not mind keeping her company this once.

He only freaked out when a week later she was still listless and her fever suddenly soared.

The doctor was again sent for.

"I'm going to put her on another medicine." Dr. Kahn told him. "It will bring her fever down but it's going to make her a little woozy. The effects would be pretty immediate." she told both Mark and Derek the dosage and the timing, and watched as she poured out her first dosage.

"You could be a nurse." teased Dr Kahn, as he persuaded Addison to swallow the noxious smelling medicine. "You're very lucky to have such good friends to take care of you." she said to Addison.

She scrunched up her nose. "I am his Red," Addison said importantly, pinching Mark's cheek. "Aren't I?"

"I guess the wooziness is kicking in." he observed as he pry each of her fingers off his face.

"I'll leave you to it." the doctor concluded.

"Mmmm." she murmured a few minutes later, squirming distractingly on the bed. "I feel wonderful. I'm much better already." She kept shifting and twisting around, making the bedsheets bunch up and the straps of her nightgown fall down.

"You need to get some sleep."

"Not until you admit that I'm your Red." Addison chided, the effects of the medicine obviously making her garrulous.

"You're my Red." Mark went along with it as Derek tried to tuck her back into bed.

"And you love me." she challenged.

He hesitated - Derek is in the room, he wanted to hiss that at her - and glanced at his best friend, who didn't look at all bothered or the very least suspicious.

 _Wouldn't that just be a awfully weird thing to say with him so very right there?_

"You don't need any more love. The whole world already loves you."

She pouted. "Say it."

"Why?"

There was a pause as Addison appeared to think hard about the question. "Because out of the whole world you're who I want to hear it from the most." she finally said.

Derek then batted at him to quickly say whatever she wanted to hear so she could get some rest.

"I love you."

She smiled angelically. "I love you too. I love you better than Savvy, and Daddy, and ..."

 **XXX**

Back in the car, Mark coolly regarded Addison.

"Did you mean it?" she asked.

That was not what he had expected her to say. He had thought she would laugh it off, or say she'd been hysterically sick and rambling on about nothing.

He didn't make himself vulnerable, though.

"Did you?" he returned.

"You're one of my best friends," Addison said, rolling her eyes. "Of course, I love you."

Mark grinned. "In that case I adore you – from the top of your redhead to the tip of your perfectly painted toes. Even when you're drunk or sick. Actually, maybe especially then."

She gave Mark a shove and he pushed her back, the movement prompting Derek to finally pull off his headphones.

"What's up?" he asked.

"Nothing." Mark laughed as Addison hit him again. "Just your girlfriend telling me how much she loves me."

* * *

 _ **So what do you think about this chapter?**_

 _ **If you guys have any suggestions for Derek please let me know and leave a review!**_


	3. (3)

**A** **How To Know Guide for Derek Shepherd:** Ways to know if your significant other and best friend are into each other. . . .

* * *

 _#3_

Oddly enough, one clear indication that your girlfriend and best friend are into each other is if they have secret emergency codes they use with one another when they need help.

Derek and Addison were walking in the park discussing and calculating his chances of graduating with honours and the likeliness of it as a result of his latest GPA when she got a text from Mark.

It was slim, he reckons. He needed a solid 4.0 this semester and unless he aces all his subjects, which, he have to agree on, is highly improbable, he'll have no choice but to graduate as common as everyone else.

Derek read the text over her shoulder, but the simple message - ' _Come quick. Code 306._ ' meant nothing to him.

She rolled her eyes and looked mildly annoyed but nevertheless quickly replied back - ' _Be right there._ ' before shoving her phone in her bag and turning to him with a sigh.

"Sorry, sweetie. But I have to go over to Mark's now." she said in a brooding voice, already heading for the road at a fast trot.

"Oh, I'll come with you." he replied easily. "It's been a while since I hung out with my boy."

Addison's mouth tightened slightly. "Alright. And please don't call him your _boy_. It's making me nauseous." she responded grudgingly, light tone gone. "But you won't be able to come up straight away when we get there."

"Why not?" he questioned suspiciously, eyebrows drawing together in a typical Derek look of confusion.

She emitted another frustrated sigh. "Never mind. There's no time in explaining now." she replied impatiently, breaking into an almost run as they crossed the street to Mark's.

After they reached the outside of his apartment, she opened her bag again and pulled out a small pillbox. When she opened and reached inside the box, he was surprised to see her pull out a glittering ring which she promptly slipped onto the _third_ finger of her left hand.

"Okay, wait down here. When you see a girl rush out the door crying or muttering obscenities, it should be safe to come up." she informed him matter-of-factly.

Before he had time to answer she had given him a quick peck on the lips and spun around to run into the building.

Derek groaned. Lately he had felt so distant from both Addison and Mark. This certainly wasn't the first time he didn't have a clue what was going on in her head. The sad thing was that he was actually pretty apathetic about finding out. It was more than just him having his mind on school and work, because he thinks something between him and Addison had shifted. She seemed to have become a different person - less bookish, a lot less studying than before but somehow still getting straight-As, more drinking and partying, even more than the daily Montgomery standard, getting strange messages from his best friend. It was like he didn't even know her anymore.

But he suspected Mark did. They have been hanging out a lot lately since he've been spending most of his time peering into his textbooks. Not that it worried him. If anything it was a relief to have the pressure of pleasing his girl taken off him for a little while. And he knew nothing would ever happen between the two of them. They were polar opposites. Addison wanted a prince, not a playboy. And Mark preferred women with a lot more experience and without inhibition and a moral compass.

As Addison had predicted, within ten minutes a girl rushed through the doors of the lobby, blonde hair flying behind her as she muttered ' _bastard, that asshole bastard_ '. Obviously, Mark was up to his usual tricks.

He assumed it was now safe for him to head on up. When he exited the elevator on Mark's floor he could already hear the sound of his girlfriend's voice. The door of Mark's apartment had been left slightly ajar.

"... And I can't believe you keep making the same stupid mistakes and just expect me to drop everything to help you out. I was having a lovely walk in the park with Derek and you know how little time we've got to spend with each other lately ..."

He felt a tiny twinge of guilt at that because truthfully, he wasn't exactly that entirely busy. He really could have spend more time with her, but it has just become so hard to, especially when half the time he was with her he can't help but think how he could be bettering his grades. Because, really, it's her fault that he's been distracted; she's his distraction.

Mark's voice suddenly cut across his girlfriend's angry tone. "Hey, how was I supposed to know she'd get all clingy and refuse to leave in the morning. I'm telling you that one needs a room at the Ostroff Centre, I thought she was going to go Glenn Close on my ass."

He heard Addison snort.

"Mark, face it, any girl who falls for your bull is probably suffering some serious mental problems. But you should know by now it's always the blondes that are the real crazies. Every single time."

"Mmm, maybe in the future I should stick to redheads." Mark drawled, his tone obviously suggestive in a way that gave Derek just the briefest pause. "What'd you say, huh, Red?"

"Ugh!" she responded. "Anything that will keep you from interrupting my mornings."

When Mark spoke again he sounded slightly irritated. "Oh, God forbid I interrupt a date with Derek the Great. It must have been so romantic given the speed with which you arrived at my front door. What, did he bore you with more of his desperate need for a higher GPA?"

There was a pause inside. Derek could picture Mark smirking at Addison as she glared at him.

He knocked on the door as he entered. Mark and Addison immediately broke from their intense stare, and an undefined tension that was hanging in the air was suddenly broken.

"Hey, I saw the blonde leave so I figured it was safe to come up." he said.

"Good to know she isn't hanging around in the lobby. It gets a bit awkward, after a while, having to ring down to reception to make sure they're really gone." Mark declared, mouth quirked.

"So, is one of you going to tell me what's going on? What the hell is a code 306?" he asked, faintly irritated.

"Number 306 of the Addison and Mark Code is invoked when one of _my_ guests proves more ... tenacious, than usual." Mark answered.

"The Addison and Mark Code?" he queried, torn between exasperation and amusement and irritation.

"A list of codes we constructed one night while you were off studying somewhere, intended to get us out of any awkward situation." Mark explained. "And we might have been slightly intoxicated while ... just to be clear."

"And each possible event from which one of us that might need restriction has a number for texting purposes, and also an innocuous phrase, a safe words - you might say - in case it needs to be dropped innocently into conversation whilst others are present." Addison further clarified. "For instance, the other night at the van der Pol wedding reception when that _Spitty_ from Genetics was threatening to dance with me I mentioned how much I enjoyed the Superman franchise as Mark happened to walk by."

"Which of course meant she needed rescuing and wanted me to fly her to a galaxy far, far away," Mark concluded.

"Right." Derek said, brows furrowing. "That's when you two disappeared out onto the balcony with a bottle of champagne and a tray of hors d'oeuvres, leaving me to be propositioned by a middle-aged and very very persistent cougar, by the way. But what was this morning's SOS about? And why is Addie carrying around a ring in her bag?"

"Because in the event of a 306, when Mark can't get one of his weak-headed mistakes from the night before to take a hint and depart in the morning, I appear on the scene wearing a ring, doing a very convincing impression of the extremely outraged and possibly violent fiancée." she spoke clearly, as if explaining the situation to a very young child.

"Speaking of which, you didn't need to hit me quite so hard earlier, Montgomery." Mark muttered, rubbing his jaw at the memory.

"You wanted it to be credible, didn't you?"

"Well, thank you so much, love." Mark bit out sarcastically.

"Save it. You can repay me by handling a 215 for me next week." Addison replied casually as she shouldered her bag and headed for the door.

"A 215?" Derek asked, as he took in Mark's blanched expression.

"Trust me. You don't want to know." Mark whispered hoarsely, as he watched Addison's swaying hips as they disappeared out his door.

Derek realised that that was true.

Even though he probably should.

* * *

 ** _A little Maddek silliness._**

 ** _What do you think?_**


	4. (4)

**A** **How To Know Guide for Derek Shepherd:** Ways to know if your significant other and best friend are into each other. . . .

* * *

 _#4_

There's a definite chance your wife and best friend are interested in each other if _he_ is the one she asks to do husband-like things, such as picking her up from the airport.

After calling in sick to work for the first time since starting at New York Presbyterian as a resident, Derek directed the driver to take him to JFK airport. He was going to surprise Addison by picking her up after her two-week vacation in Provence to visit her ailing grandmother.

It's usually a Montgomery affair but this particular year, none has the time or ... well basically, interest of going through the hassle of visiting a fragile old lady on the other side of the planet.

But since the nurses in care of Florence Montgomery, had said that things weren't looking good at all and that it might be soon now, Addison didn't want for grandmother's - what last few weeks or months she had left to be a lonely one, ergo she opt to pay her a visit on her own and make sure she'd have a greet two weeks.

The decision to meet her at the airport was part of his resolution to re-commit himself to their marriage. He had wanted to make the most of her time away by using it to determine whether he really wanted to be with her, knowing he couldn't keep stringing her along while he was only pining after his career.

Because after all, Addison is a wonderful girl and she deserves a husband who'd give her his full attention.

 _No_ ... but he also realised he had really _really_ missed her while she was away.

Maybe not as much as he suppose a husband should ... He cut that thought off in its tracks.

She's the perfect wife. And she's sweet and understanding and affectionate. She works hard to try to make him happy, to fit her needs around his, so they wouldn't have to compromise or settle or even argue.

She is the better spouse.

Though she's as busy as he is, she still manages to make time for him and their marriage, to keep their wadding spark alive. Unlike him, who has a one-track mind, and can't exactly multitask outside of the OR.

But, nevertheless, she is the perfect wife, made a point of doing all the things a wife was supposed to.

Like accompanying him to and from the airport.

She'd always done this, going with him or coming to meet him so that they could have a big Hollywood moment kiss at the terminal, a memory to take with him when he went away, or something to welcome him back again.

He'd never taken her to the airport. Or picked her up. Selfishly, the thought had never occurred to him.

It wasn't that it was really that necessary.

Addison's the kind of person who likes to be hands-on on what she does; she's organised, she's responsible, she's a lone wolf, so it's only evident that she'll handle all arrangements and plannings on her own on every trip and she is quite capable of getting herself around anyway.

Actually, she's a force to be reckoned with when it comes to cab drivers who would try to make a fool out of her and take a longer route than was strictly necessary, her sharp words quickly causing them to change direction and knock down the cost of the fare.

And Addison had never actually asked him to pick her up or drop her off any time she was going away.

But Derek knew she probably would have liked it if he had done it.

She shouldn't have to ask him.

He is her husband.

He smiled as he entered the airport.

 _Well, he is here now._

He checked the arrivals board and saw that he had fifteen minutes before Addison's plane would land. It would probably take him that long to walk to the arrival gate.

He set off, still grinning, thinking about Addison's surprised face when she sees him. It would definitely be a romantic moment, just the right thing to get their marriage back on track again. Even if he would rather be at the hospital, cutting, suturing and closing.

But as he arrived at the gate, he recognised a familiar figure. The back of the head was non-descript enough, but Derek knows of only one man in the city with the brovado to wear a vintage leather jacket like he does.

His best friend is here.

It is conceivable of course that Mark Sloan is here to greet another person arriving off the plane, but that possibility never even entered his head. The moment he saw him, Derek knew Mark had come to pick up his wife.

And though there was nothing ostensibly wrong with it, still he felt a slight swooping sensation in his stomach.

Perhaps Mark had decided to surprise her as well.

Derek walked over and tapped him on the shoulder, saluting him with an affable smile.

Mark turned around, his face betraying momentary complete and utter astonishment, as well as something else less easily defined. ( _Disappointment, maybe?_ ) But his features were quickly rearranged into his customary carefully blank canvas, assessing expression by the time he spoke.

"Hey, man." he grinned, tone friendly.

"Derek." Mark responded pleasantly. "I'm surprised to see you here. You never pick Addison up."

Derek cringed.

So, other people had noticed his slacking and failing in this respect too. It made him feel even more guilty and conscious of his neglect of Addison.

 _Why hadn't Mark ever said anything to him?_

His best friend wouldn't have been out of line telling him that it would be appropriate if he made the effort to meet his wife at the airport every once in a while.

"Yeah, I know." Derek acknowledged shame-facedly. "I thought I'd surprise her."

Mark nodded, eyes narrowed. "Oh, you will definitely do that. She asked for me to give her a ride home before she left."

Derek felt even more mortified, then.

He'd always assumed Addison would just get a cab home. That she had felt so insecure in his affections that she had organised a lift from Mark rather than relying on her husband - it was appalling.

"Oh, I didn't know." Derek said awkwardly.

"Well, you must be eager to see her again, after all this time apart," Mark tested shrewdly. "Even though you obviously don't spend the time you are together to good use, seeing that you're always at the hospital." he teased.

One more evidence to be listed in the reasons why he'd the worst spouse in the planet.

"Of course I missed her, that's why I'm here." Derek agreed. "She is, in fact, _my_ wife." he said, rolling his eyes.

Mark's lips quirked in a half-smile. "Actually Shepherd, I can understand your feelings perfectly. It will be good to have Red back. The city isn't the same without its queen."

Their conversation was interrupted as the passengers began disembarking off the plane. Derek and Mark both spotted Addison who, as she was riding in first class, was one of the first to descend the gangway.

She began walking towards them, elegantly attired for travel in a red knee length skirt that hugged her thighs and a white and red blouse that betrayed just the slightest hint of cleavage.

The effect was only marred by the slight crease in her forehead as her eyes searched the airport. However, when they finally settled on Mark, her face broke into a delighted smile.

"Punctual as ever, Mark." she smirked as she approached him. "I'll have to give you a very good tip this time. I had to buy two extra suitcases to carry all the new clothes and books my grandmother bought me."

She had not even noticed Derek, who was standing off to the side.

"Well, the vacation obviously suited you, Addie. You look even more ravishing than when you left." Mark drawled suavely.

"That might be because when you dropped me off, it was five o'clock in the morning and I was sleep deprived." she answered, rolling her eyes.

Startled by the news Mark had also dropped Addison at the airport, Derek moved forward to attract her attention.

"Derek!" she cried in shock. For a moment she merely looked baffled, but then she threw her arms around him.

After a couple of seconds, he cautiously returned her embrace, although he did not quite match her enthusiasm.

"I can't believe you came to pick me up." she said as she eventually let go.

He gave a smile that did not quite reach his eyes. "I didn't know that you had already arranged a lift from Mark."

For a second Addison looked almost embarrassed.

"Oh, well, I always ask Mark." she explained, a little flustered. "Cabs and normal cars can't always hold all my luggage. But of course Mark has the stretch."

"Plus, I do love to be the first to hear all the scandalous details of Addison's trips away." Mark contributed with a knowing smirk.

She shot him a warning glance. "They're never that scandalous, given that I have a husband." she answered glibly.

"Yes, a husband who's missed you and is very glad to have you home." Derek picked her up and kissed her once more, to Addison's delighted laughter.

When he put her down, he saw that Mark had edged off to the side, his eyes carefully averted. With his face turned away, Derek couldn't see the slightly jealous expression suffusing Mark's countenance at the public display.

"Well, as you two love birds obviously have all sorts of catching up to do, I'll leave you to it. Addison's excess luggage can of course ride home with me." Mark informed them with an agreeability he did not completely feel.

"Thanks man." Derek answered, hugging Addison to his side.

Derek very much enjoyed the ride back into town with Addison. The only moment of disquiet he experienced came after they had arrived back at their brownstone, and Mark had removed her baggage from his car.

Addison had suddenly left his side to blithely trot over to the car, tapping on Mark's window.

He obligingly rolled it down.

"You want me to check out your holiday pictures or something, Red?" Mark queried, his sarcasm downplayed by his smile.

"No, I just want to thank you for coming to pick me up." she responded coyly.

"I'll always pick you up. But I'll be collecting on that tip you promised next week." Mark murmured suggestively.

He cast a quick look in Derek's direction before whispering so only Addison could hear, "Some time when your husband's not around." He winked before rolling up his window.

Addison ran back to her husband, trying to ignore the fluttery feeling in her stomach and the momentary, unexpected wish that Mark wasn't kidding.

* * *

 ** _Another little silly Maddek madness._**

 _ **Do** **you guys think Derek is the kind of guy who wouldn't pick his wife (as in when Addison was his wife, not Meredith) up from the airport?**_

 ** _Let me know your thoughts._**

 _ **Oh and please check out my other stories, they're called -** Karma **and** Find Your Voice_


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